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Development of analytical techniques for the extraction, separation and determination of organomettalic and inorganic metal species in environmental and biological matrices.

By Raimund Wahlen

Abstract

Existing methodologies for the separation and detection of organotin species by liquid- and gas-chromatography coupled to inductively coupled plasma mass-spectrometry (ICP-MS) have been improved significantly. The LC separation of dibutyltin (DBT), triphenyltin (TPhT) and unidentified species in mussel tissue has been enhanced in terms of peak shape and resolution. GC-ICP-MS detection limits for organotin species are significantly reduced by addition of oxygen or nitrogen to the ICP-MS carrier gas. A comparison of LC-ICP-MS and GC-ICP-MS for the species-specific isotope dilution determination of tributyltin (TBT) in sediment extracts has shown that both methods deliver accurate results. However, GC-ICP-MS is significantly more sensitive (absolute detection limit of 0.03 pg TBT as Sn compared to 3 pg TBT as Sn by LC-ICP-MS) and provides superior isotope ratio measurement precision, which is linked to more reproducible peak integration and greater analyte signals by this technique. [sup]117Sn enriched DBT and TBT have been used to investigate the stability of species during extraction and the derivatisation efficiency of ethylation. The speciation of arsenic (As) has been performed using anion-exchange chromatography coupled to ICP-MS detection. Good separations have been achieved for up to seven species including monomethyl- and dimethylarsinic acid (MMA and DMA) and especially between arsenobetaine (AsB) and arsenite (As(III)). The accuracy and precision of the methods have been tested by analysis of a range of biological certified reference materials. Extraction methods for organotin and arsenic species have been developed using accelerated solvent extraction (ASE), and this technique has been assessed for the simultaneous co-extraction of Sn, As and Hg species from environmental samples. Accurate data were obtained for DBT, TBT, AsB and DMA in a certified oyster tissue, and promising results were also obtained for methylmercury. The combined extraction, separation and detection methods have been used to determine the vertical profiles of organotin and arsenic species in sediments from the Thames estuary (UK). Vp to nine organotin species were detected, with DBT being the predominant at levels ranging from [tilde] 12 - 160 ng/g (as Sn). The main As species were As(III) and As(V) at concentrations between [tilde] 160 - 4200 ng/g (as As). Methylated arsenicals were also detected throughout the core

Topics: chemistry
Publisher: Kingston University
OAI identifier: oai:eprints.kingston.ac.uk:20722
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